Scrap aluminium from foil or drinks cans can be melted down using a propane blowtorch. The metal has a melting point of 649 degrees Celsius (660 degrees Celsius), but ordinary propane blowtorches produce flames twice that temperature. Impurities such as paint form a scum called dross which is skimmed off. The molten aluminium can be cooled in steel moulds and stored as ingots for later use. The entire process is performed outside on the ground for ventilation and to avoid scorching surfaces.
Fill a large glass bowl with ordinary sand. Sand is an insulator and will protect the bowl and ground from the torch heat.
Place the bowl on a flat piece of ground outside. The bowl should be stable, and the area should be well ventilated because melting aluminium can give off toxic fumes as its impurities burn.
Push a steel cup into the sand. The edge of the cup should still be visible, but it should be almost entirely submerged in the sand and stably supported.
Compact your scrap aluminium pieces as small as possible. Squash foil into a ball and crush cans. This helps the metal melt more easily.
Put one piece of aluminium scrap inside the steel cup. The cup acts as a "crucible" when you melt the aluminium with the blowtorch.
Heat the piece of scrap with the blowtorch until it melts. As the first piece melts, add more pieces of scrap metal. The more molten aluminium there is in the crucible, the faster the new pieces of scrap will melt.
Skim any scum off the top of the aluminium with a steel ladle. Leave this to cool before discarding.
Use long-handled pliers to pick up the crucible after all the scrap is melted. Pour the aluminium into steel muffin tins. When cool, these ingots can be stored for later use.
Do this in a controlled environment where you will not be interrupted, molten aluminium is very dangerous. Never handle any of the equipment after use until you are certain it has cooled sufficiently. When using a blowtorch keep a bucket of cold water at hand in case you need to douse any unexpected flames.